Java 设置大小不影响按钮的大小

我有一个示例代码：

import java.awt.*;
import javax.swing.*;
import javax.swing.border.BevelBorder;

public class AWT extends JFrame {

    public static void main(String[] args) {
        final JFrame frame = new JFrame();
        frame.setPreferredSize(new Dimension(600, 450));
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setBackground(Color.green.darker());

        Button btn_1 = new Button("Button 1");
        btn_1.setBackground(Color.green.darker());
        btn_1.setSize(40, 100);
        Button btn_2 = new Button("Button 2");
        btn_2.setBackground(Color.green.darker());
        btn_2.setSize(40, 100);
        Button btn_3 = new Button("Button 3");
        btn_3.setBackground(Color.green.darker());
        btn_3.setSize(40, 100);

        JPanel players = new JPanel(new GridLayout(1, 3));
        players.add(btn_1);
        players.add(btn_2);
        players.add(btn_3);
        players.setBackground(Color.green.darker());
        players.setPreferredSize(new Dimension(450, 80));

        JPanel game = new JPanel();
        game.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));
        game.setBackground(Color.green);
        game.setPreferredSize(new Dimension(600, 370));

        JPanel content = new JPanel();
        content.setLayout(new BorderLayout());
        frame.setContentPane(content);
        content.add(players, BorderLayout.NORTH);
        content.add(game, BorderLayout.SOUTH);
        frame.pack();
 frame.setVisible(true);
    }
}

因此，这给了我这样一个窗口：

，而它的结果应该更像这样：

---

为什么不以这种方式渲染？

GridLayout忽略按钮的首选大小。替换

JPanel players = new JPanel(new GridLayout(1, 3));

与

附录：下面是一个让布局和默认首选尺寸发挥作用的相关示例。通过指定尽可能少的约束，调用

pack（）

时，外观会根据每个平台的外观进行调整

import java.awt.*;
import javax.swing.*;
import javax.swing.border.BevelBorder;

public class AWT extends JFrame {

    public static void main(String[] args) {
        final JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel players = new JPanel();
        players.add(new GameButton("Button 1"));
        players.add(new GameButton("Button 2"));
        players.add(new GameButton("Button 3"));
        players.setBackground(GameButton.color);

        JPanel game = new JPanel();
        game.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));
        game.setBackground(Color.green);
        game.setPreferredSize(new Dimension(600, 450));

        JPanel content = new JPanel();
        content.setLayout(new BorderLayout());
        frame.setContentPane(content);
        content.add(players, BorderLayout.NORTH);
        content.add(game, BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }

    private static class GameButton extends JButton {

        private static final Color color = Color.green.darker();
        private static final Font font = new Font("SanSerif", Font.BOLD, 20);
        private String name;

        public GameButton(String name) {
            super(name);
            this.setBackground(color);
            this.setFont(font);
        }
    }
}

GridLayout将直接添加到构件中的构件展开。我会使用另一个布局，或者如果您真的想要GridLayout，请检查下面的代码

您还必须在按钮上使用setPreferredSize！（见下文）

---

对于布局来说，这也是一个很好的解决方案。虽然setPreferredSize做了魔术中的大小部分。这很有启发性，但我经常尝试避免使用组件属性的手太重。在某些平台上，例如Mac OS X，

JButton上的
setBackground（）
没有明显的效果；而
setPreferredSize（）
无法考虑平台特定的字体度量。
import java.awt.*;
import javax.swing.*;
import javax.swing.border.BevelBorder;

public class AWT extends JFrame {

    public static void main(String[] args) {
        final JFrame frame = new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel players = new JPanel();
        players.add(new GameButton("Button 1"));
        players.add(new GameButton("Button 2"));
        players.add(new GameButton("Button 3"));
        players.setBackground(GameButton.color);

        JPanel game = new JPanel();
        game.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));
        game.setBackground(Color.green);
        game.setPreferredSize(new Dimension(600, 450));

        JPanel content = new JPanel();
        content.setLayout(new BorderLayout());
        frame.setContentPane(content);
        content.add(players, BorderLayout.NORTH);
        content.add(game, BorderLayout.CENTER);
        frame.pack();
        frame.setVisible(true);
    }

    private static class GameButton extends JButton {

        private static final Color color = Color.green.darker();
        private static final Font font = new Font("SanSerif", Font.BOLD, 20);
        private String name;

        public GameButton(String name) {
            super(name);
            this.setBackground(color);
            this.setFont(font);
        }
    }
}

import java.awt.*;

import javax.swing.*;
import javax.swing.border.BevelBorder;

public class AWT extends JFrame {

public static void main(String[] args) {
final JFrame frame = new JFrame();
frame.setPreferredSize(new Dimension(600, 450));
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setBackground(Color.green.darker());

Button btn_1 = new Button("Button 1");
btn_1.setBackground(Color.green.darker());
btn_1.setPreferredSize(new Dimension(40, 100)); 

Button btn_2 = new Button("Button 2");
btn_2.setBackground(Color.green.darker());
btn_2.setPreferredSize(new Dimension(40, 100)); 

Button btn_3 = new Button("Button 3");
btn_3.setBackground(Color.green.darker());
btn_3.setPreferredSize(new Dimension(40, 100));    

GridLayout layout = new GridLayout(1, 3);
JPanel players = new JPanel(layout);
JPanel cell1 = new JPanel();
cell1.add(btn_1);
cell1.setBackground(Color.green.darker());
players.add(cell1);
JPanel cell2 = new JPanel();
cell2.add(btn_2);
cell2.setBackground(Color.green.darker());
players.add(cell2);
JPanel cell3 = new JPanel();
cell3.add(btn_3);
cell3.setBackground(Color.green.darker());
players.add(cell3);
players.setBackground(Color.green.darker());
players.setPreferredSize(new Dimension(450, 80));

JPanel game = new JPanel();
game.setBorder(BorderFactory.createBevelBorder(BevelBorder.LOWERED));
game.setBackground(Color.green);
game.setPreferredSize(new Dimension(600, 370));

JPanel content = new JPanel();
content.setLayout(new BorderLayout());
frame.setContentPane(content);
content.add(players, BorderLayout.NORTH);
content.add(game, BorderLayout.SOUTH);
frame.pack();
frame.setVisible(true);
}
}